Interpretive Summary: The diamondback moth (DBM) is the most serious pest of cruciferous crops worldwide, with control costs alone estimated at $1 billion annually. Bombardment of DBM with pesticides has resulted in the development of resistance to all major groups of insecticides including insect growth regulators and biological pesticides. Scientists at the Center for Medical, Agricultural and Veterinary Entomology, Gainesville, Florida, are developing alternative strategies for managing DBM in cabbage that de- emphasize use of costly, environmentally polluting conventional insecticides while promoting the use of natural enemies and modification of cultural practices. Under investigation is the use of nursery sites in the field stocked with DBM larvae to produce large numbers of parasitoids such as Cotesia plutellae, an exotic species that has shown promise as a control agent for this pest. Laboratory and field cage studies were conducted to determine if C. plutellae wasps would parasitize sterile DBM larvae equall as well as normal larvae. If so, the sterile larvae could be used as hosts in the field. Any larvae that escaped parasitism and emerged as adults would be harmless to the crop as the adults also would be sterile. Results showed that parasitism, foliage consumption after parasitism, and survivorship were similar for normal and sterile DBM larvae. Also, female wasps that developed from sterile larvae were as fit as females that developed from normal larvae. Use of sterile DBM larvae in augmentative parasitoid release programs of this type not only could provide hosts to increase parasitoid numbers, but potentially could contribute another measure to control of DBM populations through mating of sterile male moths from larvae that were not parasitized with normal, wild DBM females.

Technical Abstract:
The ability of the Braconid endoparasitoid Cotesia plutellae (Kurdjumov) to accept and develop successfully in normal and sterile Plutella xylostella (L.) larvae was evaluated. Cotesia plutellae does not discriminate between larvae sterilized by gamma radiation and normal larvae, and both sets of larvae serve as suitable host for the parasitoid. Data for parasitism, foliage consumption and survivorship were similar for the two types of larvae. Adult female F1 parasitoids developed from sterile diamondback larvae were as fit as those from normal larvae. In laboratory bioassays, sterile and normal diamondback larvae traversed similar distances before pupation. Field cage assays showed less distance traversed by both types of larvae compared to the laboratory studies. Survivorship for both types of larvae was very low under field conditions.